Not offering As-Salat (the prayers) at its stated fixed time
حَدَّثَنَا عَمْرُو بْنُ زُرَارَةَ، قَالَ أَخْبَرَنَا عَبْدُ الْوَاحِدِ بْنُ وَاصِلٍ أَبُو عُبَيْدَةَ الْحَدَّادُ، عَنْ عُثْمَانَ بْنِ أَبِي رَوَّادٍ، أَخِي عَبْدِ الْعَزِيزِ قَالَ سَمِعْتُ الزُّهْرِيَّ، يَقُولُ دَخَلْتُ عَلَى أَنَسِ بْنِ مَالِكٍ بِدِمَشْقَ وَهُوَ يَبْكِي فَقُلْتُ مَا يُبْكِيكَ فَقَالَ لاَ أَعْرِفُ شَيْئًا مِمَّا أَدْرَكْتُ إِلاَّ هَذِهِ الصَّلاَةَ، وَهَذِهِ الصَّلاَةُ قَدْ ضُيِّعَتْ. وَقَالَ بَكْرٌ حَدَّثَنَا مُحَمَّدُ بْنُ بَكْرٍ الْبُرْسَانِيُّ أَخْبَرَنَا عُثْمَانُ بْنُ أَبِي رَوَّادٍ نَحْوَهُ.
Narrated Az-Zuhri that he visited Anas bin Malik at Damascus and found him weeping and asked him why he was weeping. He replied, "I do not know anything which I used to know during the life-time of Allah's Apostle except this prayer which is being lost (not offered as it should be)."